mahmood zobeiri

In this research، we tested biasedness of canopy cover and density estimation of forest trees and shrubs by the use of line sampling method. For this aim، locations and crown width of all trees and shrubs with crown width more than 10 cm in a 53 ha forest area in Ardal located in Chahar-Mahal and BakhtiariProvince were recorded. Then، 100 segments of line transect with various length (50، 100، 150، 200، 250، 300، 350 and 400 meter) were sampled، and this procedure was repeated 100 times. We used ANOVA to see if there is any significant differences between the estimated forest density and canopy cover with the different transect length. Results showed that، there is no statistical significant difference between various transects length for both variables. Also، as could be expected، by increasing the length of transects، the coefficient of variation was decreased and this decrease were negligible for transects longer than 200 m. This means no more precision could be achieved by more effort on measuring sample lines longer than 200 m. Analysis showed that the line transect sampling method is biased (over estimate) and the average relative bias were between 4-6 and 6-10 percent for tree density and crown coverage، respectively. Based on results، it can be claimed that، by considering the ease and speed of transect sampling method، the bias of estimates are negligible.

Mountainous forest communities of Irano-Turanian vegetation region are characterized with Juniperus excelsa. These forests have involved too many changes in the past and nowadays mostly are not integrated. But there are still some dense or broad stands. In this research، we have studied such these communities and their ecological properties in north of Tehran to northwest of Semnan province. A data set including floristic data according to Braun-Blanquet method and environmental variables were provided. To classify the vegetation، TWINSPAN and analyzing vegetation data with JUICE، and to investigate the species-environment relationship، ANOVA and Ordination (CCA and PCA) was used. According to the results، the vegetation was classified into six groups which were specific in floristic composition and ecological characteristics، and were described by their site properties، constant and indicator species. These groups took placed in three forest communities: Juniperus excelsa - Rhamnus pallasii، J. excelsa - Cotoneaster nummularius and J. excelsa - Lonicera iberica. The first one is significantly related to lower altitude and soils with poor nitrogen and organic matters، the second community is interested in upper lands and nutrient soils with a high saturated water capacity and the third one comprises stands impressed by the moist climate of the Hyrcanian region.

The aim of this research was to determine the number and volume changes after the implementation of a 10 years forest management plan period and comparing of these changes with the aimed purposes. Inventories have been done systematic random sampling in 1000 m2 area plots. Diameter at breast height، control trees height and quality of first 6 m trunk length of trees with dbh more than 42. 5 cm is measured and estimated. Volumes of inventoried trees were calculated based on forest management plan Taryf. To compare the mean volume and number of trees per hectare in the two inventories volume table، t test was aplicated. In order to compare trees height curves at the beginning and end of period، cloud points of control trees was drawn and then modeling with regard to it. The results showed that during the implementation، mean volume has increased 10 sylves per hectare and 47 trees has decreased in hectare، but these changes were not significant regarding to t test (d. f=32، P<0. 05). After implementation، the height curve of tress and volume of trees with high degree of quality has increased. Percent volume per hectare of beech species is passed from planned mode (ideal mode) and the species hornbeam and oak nears to ideal mode. The other species have not only failed to approach the ideal goals، but also we are far from it. Reforestation rate performed is almost 50 percent of planned.

For maintaining of Zagros forests role in wild life, water and soil conservation, the suitable solutions and methods for assessing the existing conditions and planning for management of this forests should be given. To detection of suitable sampling method to study tree density in the northern Zagros forest, Blake forest, in Baneeh region, Kurdistan province, and west of Iran was selected. 40 square sample plots one hectare (100×100 m) were selected and perfect inventoried. In every sample plot the position of tree, kind of species and number of species were recorded. In order to study of tree density (tree/ha) different sampling methods (rectangular sample with 20×50 m and 10×50, random sampling method with 40, 50 and 60 circle sample plots which everyone was 1000 m2) compered the prefect inventory. To determination of suitable sampling for study of tree density used the %E2 ×T indexes. To compere the tree parameter in the every sampling methods and perfect inventory used the t-test analysis. Data analyzing was done by SPSS16 software’s. Results showed that the rectangular sample with 20×50 m sample methods was the best methods and have maximum of accuracy. Overall results showed that the rectangular sample with 20×50 m sampling methods was (have minimum of time and %E2×T criteria) the suitable methods to study of density (tree/ hectare). Authors suggested to study of tree density (tree/hectare) in the northern zagros forest used the rectangular sample with 20×50 m sampling methods.